________________________________
From: maxima-bounces at math.utexas.edu
[mailto:maxima-bounces at math.utexas.edu] On Behalf Of Rogers, Raymond
Sent: Friday, January 25, 2008 2:07 PM
To: maxima at math.utexas.edu
Subject: Re: [Maxima] seeking help with solving implicit
equation
: [Maxima] seeking help with solving implicit equation
Folks,
I'm writing a routine which makes use of the Colebrook
equation for calculating friction factors:
1/sqrt(f) = -2log(e/3.7D + 2.51 / (Re*sqrt(f))
In other words, the equation is implicit in the friction
factor f.
How do I properly define the equation and solve for f
once I have defined e, D, Re? I thought it was as simple as
1/sqrt(f):= ..etc.., define the other variables via the
: operator and solve (%,f) but this makes Maxima swear at me. It seems
like this should be fairly straightforward root finding, but then again
I am not a mathematician and there's likely some fundamental problem
staring me full in the face.
A clue for the clueless?
Thanks
Len
Len de Vlaming
Project Consultant
If you expand the log
1/sqrt(f) -log(sqrt(f)) = g(e,D,Re)
which looks to be solvable as Lambert's function.
RayR
Sorry, I misparsed the equation. It's a little more complicated.
RayR
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.math.utexas.edu/pipermail/maxima/attachments/20080125/a24fb3b3/attachment.htm